x86: sanitize user specified e820 memmap values

Sanitize user specified e820 memory ranges, using the same logic that is
applied to the values returned by the BIOS.  This ensures consistent
handling regardless of the source of the memory mappings.

Allows overriding portions of the memory map without specifying one in
it's entirety (memmap=exactmap).

E.g. marking a range of bad RAM as reserved with memmap=48M$528M

BIOS supplied range

BIOS-e820: 0000000000100000 - 000000007fe80000 (usable)

becomes

user: 0000000000100000 - 0000000021000000 (usable)
user: 0000000021000000 - 0000000024000000 (reserved)
user: 0000000024000000 - 000000007fe80000 (usable)

Previously this did not work, as the original BIOS range was left
untouched while the user defined range was appended to the end of the
memory map.

[ tglx: arch/x86 adaptation ]

Signed-off-by: Vladimir Berezniker <vmpn@hitechman.com>
Signed-off-by: Andi Kleen <ak@suse.de>
Signed-off-by: Ingo Molnar <mingo@elte.hu>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>